1. Field of the Invention
The present invention relates to a structure of semiconductor device which realizes a very fine gap to be formed between a contact hole in which an upper conductive layer is formed and a lower conductive layer, and to a method of manufacturing semiconductor devices having such a structure.
2. Description of the Prior Art
In some semiconductor devices, two conductive layers (wiring or electrode layers) which shall be insulated against each other are laminated one upon another with an insulation interlayer between them. A contact hole is formed on the insulation interlayer in the vicinity of the lower conductive layer, and a part of the upper conductive wiring or electrode layer is formed in the contact hole.
Integration of this sort of semiconductor may be improved by reducing a distance between the contact hole and the lower conductive layer.
If the distance between the contact hole and the lower conductive layer is reduced, however, the insulation interlayer between the contact hole and the lower conductive layer will be thinned. As a result, an insulation property, i.e., voltage resistance of the insulation interlayer may be deteriorated due to defects, etc., in the insulation interlayer. This may cause the lower conductive layer and the upper conductive layer in the contact hole to short-circuit.
To cope with this problem, a structure is proposed to form a contact hole firstly and then a nitride film (Si.sub.3 N.sub.4) on an inner wall of the contact hole. After that, an upper conductive layer is formed on the nitride film in the contact hole. The nitride film of this structure can improve an insulation property between a lower conductive layer and the upper conductive layer formed in the contact hole.
However, the nitride film formed on the inner wall of the contact hole narrows an actual opening area of the contact hole. Therefore, to obtain the same opening area as that of a contact hole with no nitride film, the opening area of the contact hole of this structure shall be widened. As a result, the distance between the contact hole and the lower conductive layer may be reduced, but integration of the structure cannot be improved.